FIGURE 2.

Architectural parameters control the bistability. (A) A 2D defected multistable structure with a gradual transformation of unit cells from their open configuration to the closed one. This structure was produced by introducing cuts into a polymer sheet (Jin et al., 2020). (B) When a single unit cell under volumetric straining is bistable, the strain energy density exhibits two stable minima associated with the closed (${\epsilon }_0$) and open (${\epsilon }_s$) configurations. The energy density is approximated by a fourth-order polynomial characterized by the energy density barrier (I), the energy density of the open state (II), and the open-state strain (III). The unit cell’s architecture is characterized by the unit cell length L, rotating unit length a, hinge length b, and thickness c. (C) Design maps of strain energy characteristics for varying hinge and rotating unit lengths while keeping the hinge thickness constant at $c=0.025L$. (D) Double-well strain energy densities corresponding to the colored markers in the design maps of Figure 2C. (E) Design maps of bistability characteristics for varying hinge thicknesses while keeping the hinge length constant at $b=0.1L$. (F) Double-well strain energy densities corresponding to the markers in the design maps of Figure 2E.